The present invention relates to apparatus and a method for assessing the colour of gemstones and the like. The apparatus and method were developed primarily for diamonds, but may be used for other suitable stones such as other gemstones or simulants and for diamond simulants, and also for pearls--where the context admits, the terms "gemstones or the like" or "stone or the like" as used herein includes simulants and pearls.
Very small colour differences can have a large effect on the value of a gemstone, and it is important to be able to sort gemstones accurately according to their colour. The most usual method at present is for the stones to be examined visually by an expert using a lens of 10.times. magnification. This method is slow, requires considerable expertise and has relatively poor reproducibility.
Various apparatuses have been proposed, the apparatuses in general having a chamber for containing the gemstone, mounting means for mounting the gemstone, projecting means for projecting light onto the stone and detecting means for detecting the colour of the light reflected from the stone. The purpose of the apparatuses is to give objective measurements of the colour of the stone.